The present disclosure relates to digital printing apparatus, such as using xerographic or ink-jet technology, and carrying out image-quality tests therein. More particularly, it relates to an apparatus employing a shutter plate that offers protection from contamination and assist in guiding the paper through a structure such as baffle.
Image-capturing peripherals such as scanners have become increasingly useful, affordable and common devices for homes and businesses. These devices are useful for capturing and storing images such as text, graphic or pictorial images contained on documents. Various types of scanners include flatbed, drum and handheld scanners. With a flatbed scanner, one of the most common types of scanners, a document to be scanned is typically placed onto a transparent glass platen of the scanner, where a scanner head assembly (also referred to as a carriage assembly) moves to capture the image contained on the document. The image in digital form is often transmitted to a connected computer such as a database hosted by a server, though it may instead be stored within the scanner, or transmitted directly to another peripheral such as a printer or facsimile (fax) machine.
It is common to require occasional “calibration” of the printer especially in color printing using digital printers. Generally this is done by causing the printer to output sheets bearing a series of “test patches,” each patch representing a desired color. The test patches are then read by a spectrophotometer or similar image sensor, and the actual reflectance values of the patches are compared to the colors of the desired patches. In a high-speed, production context, it is known to provide image sensors immediately downstream of a printing apparatus for various purposes, as shown in U.S. Pat. Nos. 5,488,458; 6,324,353; and 6,684,035.
In practical operation, an image sensor used in combination with a printer must itself be calibrated occasionally. Sensor calibration usually involves exposing to the sensor a surface of known predetermined optical properties, such as a predetermined blackness or whiteness, and then adjusting the outputs of the image sensor accordingly. U.S. Pat. No. 6,198,536 shows a sheet scanner in which calibration targets can be slid underneath a spectrophotometer: a user manually slides the desired black or white calibration “backer” underneath the spectrophotometer as needed.
However, conventional systems tend to add contaminants on the calibration strip causing a less than optimal calibration. Poor calibration results in the quality of the output copy being unacceptable due to the system or machine software misinterpreting the reflected light and wrongly adjusting the print output. Various techniques have been adopted to remove the contaminants from the calibration strip such as the use of cleaning blades. Cleaning blades introduce problems such as scratching, warping, and the introduction of streaks on the calibration strip. To ensure repeatability of reflected light back into the scan unit during calibration the calibration strip must be prevented from being marked, blemished, scratched and scuffed. Failure to meet these criteria will result in the quality of the output copy being unacceptable due to the system or machine software misinterpreting the reflected light and wrongly adjusting the print output.
The present disclosure, in various embodiments, is directed to a system useful in calibrating image sensors, whether as part of a testing station downstream of a printing apparatus, within a scanner for recording hard-copy images, or for any other purpose.